1. Field of the Invention
The present invention relates to an induction sealing apparatus which seals a foil sheet or liner to the opening of a container and, more particularly, to an induction sealing apparatus which is air cooled and which does not require the use of thermally conductive material disposed within ferrite cores of the apparatus to facilitate heat removal.
2. Related Art
Induction sealing units for sealing and hermetically sealing or tamper-proof sealing containers with foil liners are typically included in conveyer systems for high volume applications. A discussion of the general principles of inductive sealing is disclosed in pending application Ser. No. 09/138,159, the entire contents of which is incorporated by reference.
Conventional systems comprise an induction head which includes ferrite materials arranged to channel and direct the electromagnetic field towards the foil liner. An electric current is induced in the foil liner which heats the foil to a temperature sufficient to bond the foil to the rim of the container. As the foil and rim cool, the foil is firmly joined to the rim providing a securely sealed container.
Induction sealing systems generate a significant amount of excess thermal energy and have to be cooled in some way. Some systems use water cooling while others circulate air across heat sinks to draw heat away from the core.
In air cooled systems, a thermally conductive material is disposed within the ferrite core in order to conduct the heat generated within the core to heat sinks which are used to transfer the thermal energy to the air used to cool the unit. This thermally conductive material adds to the cost and weight of the device and is subject to mechanical failure and cracking. Heat sinks are usually made of metal and are produced with a plurality of fin projections to help dissipate the excess heat produced within the ferrite core. Exposed fins are subject to breakage which reduces the effectiveness of the heatsinks. Also, the use of extensive heatsinks add to the complexity and weight of the device.
Water cooled systems are necessarily more complicated and more costly. Water cooled systems require plumbing and a pumping system to circulate the water throughout the induction sealing head.
Accordingly, the present invention provides an induction sealing unit which does not require thermally conductive materials disposed within the ferrite core and is thus less expensive to produce than the prior art.
The present invention also provides an induction sealing head which utilizes an air cooled slotted ferrite core to minimize the use of complex heat sink configurations.
The present invention also provides an induction sealing head which is more energy efficient than conventional induction sealers.
The present invention also provides an induction sealing unit that is easy to use, manufacture and maintain.
The present invention attains these features by providing a sealing unit having a horizontal mounting plate, a ferrite core having openings formed therethrough, disposed on the mounting plate and a litz wire coil disposed proximate to the ferrite core for producing an electromagnetic field. The ferrite core and litz wire coil are adapted to direct an electromagnetic field toward a foil used to seal an opening of a container. The horizontal mounting plate has openings coinciding with the openings within the ferrite core to provide air flow through and around the core and sealing head.